The present invention relates to medical imaging arts. It finds particular application to an intravascular ultrasonic image analysis method and system which determines luminal and medial-adventitial boundaries of a vascular object.
Ultrasonic imaging of portions of a patient""s body provides a useful tool in various areas of medical practice for determining the best type and course of treatment. Imaging of the coronary vessels of a patient by ultrasonic techniques can provide physicians with valuable information. For example, the image data may show the extent of a stenosis in a patient, reveal progression of disease, help determine whether procedures such as angioplasty or atherectomy are indicated or whether more invasive procedures may be warranted.
In a typical ultrasound imaging system, an ultrasonic transducer is attached to the end of a catheter that is carefully maneuvered through a patient""s body to a point of interest such as within a blood vessel. The transducer is a single-element crystal or probe which is mechanically scanned or rotated back and forth to cover a sector over a selected angular range. Acoustic signals are transmitted during the scanning and echoes from these acoustic signals are received to provide data representative of the density of tissue over the sector. As the probe is swept through the sector, many acoustic lines are processed building up a sector-shaped image of the patient.
After the data is collected, images of the blood vessel are reconstructed using well-known techniques. Since the data is acquired along a section of the vessel, hundreds of intravascular images may be generated. A typical analysis includes determining the size of the lumen and amount of plaque in the vessel. This is performed by having a user visually analyze each image and manually draw a boundary contour on the image at a location where the user believes is the luminal boundary and medial-adventitial boundary of the vessel. This is a very time consuming process which can take days to evaluate a set of images from one patient. Furthermore, the boundary determination is made more difficult when the images are of poor quality and the boundaries are difficult to see on the image.
The present invention provides a new and unique intravascular ultrasonic image analysis method and system with cures the above problems and others.
In accordance with the present invention, a new and unique method for determining a boundary contour of a blood vessel is provided. An intravascular ultrasound image of the blood vessel is generated from data acquired radially within the blood vessel by an ultrasonic device. The ultrasound image is displayed to a user where the image includes a representation of a boundary of the blood vessel. The user selects control points along the boundary. The control points are interpolated to generate a boundary contour. The boundary contour is then optimized by adjusting each of the control points based on a gradient image which includes a distinguished boundary determined from the ultrasound image.
In accordance with a more limited aspect of the present invention, the distinguished boundary is determined by radially analyzing pixel values of the ultrasound image.
In accordance with a more limited aspect of the present invention, the gradient image is formed by converting the ultrasound image to a polar image where the polar image has a plurality of radial scan lines which include a plurality of pixels. An edge of the boundary is radially determined along each of the radial scan lines by applying a gradient filter to each of the plurality of pixels. The gradient filter distinguishes pixels which likely form the edge of the boundary. The distinguished pixels defme the distinguished boundary.
In accordance with another aspect of the present invention, a method of intravascular analysis of an intravascular image is provided. The intravascular image is generated from data acquired by an ultrasonic device which radially scans a vascular object internally. The intravascular image is converted to a Cartesian format which includes a representation of a boundary of the vascular object. Boundary points are selected on the intravascular image in a vicinity of the boundary. A first boundary contour is generated based on the boundary points. A second boundary contour is then generated based on radial boundary determined performed on a polar image of a intravascular image. The first boundary contour is then adjusted by an influence from the second boundary contour to obtain an optimized boundary contour.
In accordance with a more limited aspect of the present invention, the radial boundary determination includes applying a gradient filter in a radial direction on the polar image. The gradient filter distinguishes areas of the polar image in the vicinity of the boundary of the vascular object.
One advantage of the present invention includes determining luminal and medial-adventitial boundaries from an ultrasound image using image data having the same format as the IVUS data which was collected. In particular, IVUS data is collected radially by a rotating transducer or array of transducers. Thus, to obtain a more accurate boundary determination, the boundary determination is influenced by radial edge detection from a polar format of an image.
Another advantage of the present invention is that the determination of luminal and medial-adventitial boundaries is accurately performed. Additionally, the present system reduces the time necessary for a user to determine these boundaries which may involve manually processing hundreds of images.
Another advantage of the present invention is that boundary determination can be performed in real-time, for example, in an operating room. In this manner, a surgeon can receive immediate data relating to a patient""s blood vessels.
Still further advantages of the present invention will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description of the preferred embodiments.